Wolf Creek IA 02-CED-530

mouth (S29 T87N R11W Black Hawk Co.) to confluence with Twelvemile Cr. in S19 T86N R13W Tama Co.

This is a DRAFT assessment

Draft assessments may change without notice

Open Data Collection Period Modal

For purposes of developing stream/river water quality assessments for integrated reporting, three years of water quality data are typically used for both conventional pollutant parameters (e.g., indicator bacteria) and the less frequently monitored toxic parameters (e.g., toxic metals). Since the 2004 IR cycle, DNR has used a three-year data gathering period for streams, rivers, and beaches. For most assessments, the use of three years of data increases the number of samples upon which the decision on use support is based and helps address the problem of weather-related year-to-year fluctuations in water quality.

Due to the lower sampling frequency in Iowa’s ambient lake, biological, fish kill, and fish tissue monitoring programs, five years of data are used for developing IR assessments and for identifying Section 303(d) listings.

Data Type	Data Timeframe
Beach Sampling Data	CY 2022 - 2024
Stream/River Water Quality Data	CY 2022 - 2024
Lake Water Quality Data	CY 2020 - 2024
Biological Sampling Data	CY 2020 - 2024*
Fish Kill Data	CY 2020 - 2024
Fish Tissue Sampling Data	CY 2020 - 2024
Continuous Dissolved Oxygen Sampling Data	CY 2020 - 2024
*Biological sites sampled in both 2019 and 2023 were also assessed.

Open Segment Map
View 2026 assessment summary page

Cycle: 2026
Current Phase: Public Comment
Overall IR: 5 - Water is impaired or threatened and a TMDL is needed.
Trend: Stable
Created: 10/27/2025 3:09:40 PM
Updated: 2/11/2026 10:43:43 AM

Use Support

Class A1

Presumptive Use

Recreation - Primary contact

Not Supported

Bacteria: Indicator Bacteria- E. coli

Support Level

Not Supported

Impairment Code

5p - Impairment occurs on a waterbody with a presumptive A1 or B(WW1) use.

Cause Magnitude

Slight

Status

Continuing

Source

Unknown: Source Unknown

Source Confidence

N/A

Cycle Added

2008

Impairment Rationale

Geometric mean criterion exceeded

Data Source

Ambient monitoring: Iowa DNR-rivers

TMDL Priority

Tier III

Class BWW1

Aquatic Life - Warm Water Type 1

WINOFI

Biological: low aquatic macroinvertebrate IBI

Support Level

Further Investigation Needed

Impairment Code

3b-c - Use potentially biologically impaired based on calibrated IBI metrics.

Cause Magnitude

Slight

Status

Continuing

Source

Unknown: Source Unknown

Source Confidence

N/A

Cycle Added

2022

Impairment Rationale

Potential Impairment

Data Source

Biological monitoring: Iowa DNR WQMA

Class HH

Human Health -

Fully Supported

Impairment Delistings

No delistings for this assessment cycle.

Documentation

Assessment Summary

The presumptive Class A1 use was assessed as "not supported" due to levels of indicator bacteria (E. coli) that violated state water quality criteria. The Class BWW1 use was assessed as "WINOFI" based on biological sampling data. The Class HH use was assessed as "fully supported" based on water quality monitoring data.

Assessment Explanation

Data Sources:

Data Source	Data Source ID	Data Type	Data Age	Site ID	Site Name	Site Description
Iowa DNR	6	WQ	CY 2022-2024	10070002	Wolf Creek at La Porte City
CRWQ	23	WQ	CY 2022-2024	99990048	Wolf Creek
Iowa DNR	6	BIO & WQ	CY 2021	434	Wolf Creek	La Porte City (REMAP #109)
Iowa DNR	6	BIO	See Below	1154	Wolf Creek	Main St Bridge La Porte City
Iowa DNR	6	BIO	See Below	1262	Wolf Creek	La Porte City (REMAP #402)

Presumptive Class A1 - Indicator Bacteria:

Site ID

Data Source ID

# Samples per Year (2022/ 2023/2024)

2022 Geometric Mean

2023 Geometric Mean

2024 Geometric Mean

Violates Annual Geometric Mean?

# 2022 SSM violations / SSM Violations needed for impairment

# 2023 SSM violations / SSM Violations needed for impairment

# 2024 SSM violations / SSM Violations needed for impairment

Violates Annual SSM Significantly >10% Rule?

Assessment Type

Support Level

10070002

7/8/7

540

860

326

YES

5 / 3

6 / 3

4 / 3

YES

MONITORED

NOT

99990048

5/5/5

147

182

544

YES

3 / NA

1 / NA

4 / NA

YES

EVALUATED

NOT

Presumptive Class A1 – pH:

Site ID	Data Source ID	# Samples / # Years	Minimum Value	Maximum Value	Mean Value	# Violations	Violations needed for impairment	Violates Significantly >10% Rule?	Assessment Type	Support Level
10070002	6	35 / 3	7.7	8.4	8.1	0	7	NO	MONITORED	FULL
99990048	23	15 / 3	7.82	8.49	8.2	0	4	NO	MONITORED	FULL

Class BWW1 - Binomial Parameters:

Site ID	Data Source ID	Parameter Name	# Samples / # Years	Minimum Value	Maximum Value	Mean Value	# Violations	# Acute / Chronic Violations	Violations needed for impairment	Violates Significantly >10% Rule?	Assessment Type	Support Level
10070002	6	Chloride	36 / 3	19	30	23	NA	0 / 0	7	NO	MONITORED	FULL
99990048	23	Chloride	15 / 3	17.5	32.8	22.7	NA	0 / 0	4	NO	MONITORED	FULL
10070002	6	Dissolved Oxygen	35 / 3	7.5	13.7	10.3	0	NA / NA	7	NO	MONITORED	FULL
99990048	23	Dissolved Oxygen	14 / 3	6.6	13.7	8.5	0	NA / NA	4	NO	MONITORED	FULL
10070002	6	pH	35 / 3	7.7	8.4	8.1	0	NA / NA	7	NO	MONITORED	FULL
99990048	23	pH	15 / 3	7.82	8.49	8.2	0	NA / NA	4	NO	MONITORED	FULL
10070002	6	Sulfate	36 / 3	11	53	29	0	NA / NA	7	NO	MONITORED	FULL
99990048	23	Sulfate	15 / 3	11.6	42.7	23.6	0	NA / NA	4	NO	MONITORED	FULL
10070002	6	Temperature	36 / 3	0.1	22.8	10.6	0	NA / NA	7	NO	MONITORED	FULL
99990048	23	Temperature	15 / 3	5.2	24.7	18.3	0	NA / NA	4	NO	MONITORED	FULL

Class BWW1 - Toxic Parameters:

Site ID	Data Source ID	Parameter Name	# Samples / # Years	Maximum Value	Mean Value	Median Value	# Acute / Chronic Violations	>1 Acute / Chronic Violation	Assessment Type	Support Level
10070002	6	Ammonia	35 / 3	0.27	0.05	0.02	0 / 0	NO	MONITORED	FULL
10070002	6	Cadmium	18 / 2	0.5	0.5	0.5	0 / 0	NO	MONITORED	FULL
10070002	6	Chromium	18 / 2	3	0.96	0.92	0 / 0	NO	MONITORED	FULL
10070002	6	Copper	18 / 2	4.5	1.6	1.2	0 / 0	NO	MONITORED	FULL
10070002	6	Lead	18 / 2	1	1	1	0 / 0	NO	MONITORED	FULL
10070002	6	Nickel	18 / 2	2.7	1.1	1	0 / 0	NO	MONITORED	FULL
10070002	6	Selenium	36 / 3	3.1	1.2	1	0 / 0	NO	MONITORED	FULL
10070002	6	Silver	18 / 2	1	1	1	0 / 0	NO	MONITORED	FULL
10070002	6	Zinc	18 / 2	5.8	1.2	0.5	0 / 0	NO	MONITORED	FULL

Class BWW1 - Biological Sampling:

Benthic Macroinvertebrates:

Site ID	Date	Drainage Area (mi2)	Ecoregion	Major Drainage	BM Sample Gear	BMIBI score	BMIBI Class	47c BMIBI BIT	BMIBI Pass/Fail
1154	8/15/22	326.0	47c	MS	Floating Art Sub	71	Good	52	Pass
434	9/9/21	325.9	47c	MS	Hess	55	Fair	70	Fail
1262	8/25/20	306.0	47c	MS	Floating Art Sub	49	Fair	52	Fail
1154	8/15/18	326.0	47c	MS	Floating Art Sub	81	Excellent	52	Pass

Fish:

Site ID	Date	Drainage Area (mi2)	Ecoregion	Major Drainage	Riffle Stream?	FIBI score	FIBI Class	47c FIBI BIT	FIBI Pass/Fail
434	9/9/21	325.9	47c	MS	No	57	Good	44	Pass
1262	8/25/20	306.0	47c	MS	No	61	Good	44	Pass

Overall:

Community	Assessment Type	Assessment Result	Support Level	IR Category	Reason
Benthic Macroinvertebrates	Evaluated	Fail (2/4)	WINOFI
Fish	Monitored	Pass (2/2)	Full		Assessment was evaluated because although the BMIBI assessment used
Overall	Evaluated	Fail	WINOFI	3bc	multiple samples collected in the last five years, it was inconclusive.

Class BWW1- Continuous DO Monitoring:

Site ID	Data Source ID	# Days Monitoring (2021)	DO Criteria Type	# 2021 violations / Violations needed for impairment	Violates Annual Significantly >10% Rule?	Assessment Type	Support Level
			24 hr	0/4	No
430	6	15	16 hr	0/4	No	Evaluated	Full

Class HH-F - Toxic Parameters:

Site ID	Data Source ID	Parameter Name	# Samples / # Years	Maximum Value	Mean Value	Median Value	Number of Non - Detects	Mean Value > Criterion or MCL	Assessment Type	Support Level
10070002	6	Copper	18 / 2	4.5	1.6	1.2	5	NO	MONITORED	FULL
Site ID	Data Source ID	Parameter Name	# Samples per Year (2022/ 2023/2024)	2022 Mean	2023 Mean	2024 Mean	# Non-Detects per Year (2022/ 2023/2024)	Support Level per Year (2022/ 2023/2024)	Assessment Type	Support Level
10070002	6	Selenium	12/12/12	1.125	1.042	1.417	5/5/3	FS/FS/FS	MONITORED	FULL

Monitoring and Methods

Assessment Key Dates

1/11/2022

Monitoring Start

12/9/2024

Monitoring End

8/25/2020

Biological Monitoring

9/9/2021

Biological Monitoring

8/15/2022

Biological Monitoring

9/9/2021

Monitoring Start

9/23/2021

Monitoring End

8/15/2018

Biological Monitoring

Methods

150

Monitoring data more than 5 years old

200

Physical/Chemical Monitoring

315

Regional reference site approach

320

Benthic macroinvertebrate surveys

330

Fish surveys

420

Indicator bacteria monitoring

860

Other Agencies/Organizations provided monitoring data